Semiconductor device and method for fabricating the same

ABSTRACT

A method of fabricating a semiconductor device includes forming a first gate pattern and a dummy gate pattern on a first active area and a second active area of a substrate, respectively, the first gate pattern including a first gate insulating layer and a silicon gate electrode, removing the dummy gate pattern to expose a surface of the substrate in the second active area, forming a second gate pattern including a second gate insulating layer and a metal gate electrode on the exposed surface of the substrate, the first gate insulating layer having a thickness larger than a thickness of the second gate insulating layer, and forming a gate silicide on the silicon gate electrode after forming the second gate pattern.

BACKGROUND

1. Technical Field

The present disclosure relates to a semiconductor device and method forfabricating the same.

2. Description of the Related Art

Recently, down-scaling of a semiconductor device is being advancedrapidly along with the development of electronic technology. Thesemiconductor device may include, for example, both a portion requiringa relatively fast reaction and a portion requiring a relatively stableoperation. With the down-scaling of the semiconductor device, variousstudies are being conducted on how to optimize transistors included inportions having different functions.

SUMMARY

Exemplary embodiments of the present invention provide a semiconductordevice with increased reliability by using a silicon electrode in aportion requiring stability and using a metal electrode in a portionrequiring a fast operating speed.

Exemplary embodiments of the present invention also provides a methodfor fabricating the semiconductor device.

According to an exemplary embodiment of the present invention, there isprovided a method for fabricating the semiconductor device comprisingforming a first gate pattern and a dummy gate pattern on a first activearea and a second active area of a substrate, respectively, the firstgate pattern including a first gate insulating layer and a silicon gateelectrode, removing the dummy gate pattern to expose a surface of thesubstrate in the second active area, forming a second gate patternincluding a second gate insulating layer and a metal gate electrode onthe exposed surface of the substrate, the first gate insulating layerhaving a thickness larger than a thickness of the second gate insulatinglayer, and forming a gate silicide on the silicon gate electrode afterforming the second gate pattern.

According to an exemplary embodiment of the present invention, there isprovided a method for fabricating the semiconductor device comprisingforming a first gate pattern and a dummy gate pattern on a first activearea and a second active area of a substrate, respectively, the firstgate pattern including a first gate insulating layer and a silicon gateelectrode, forming a gate silicide on the silicon gate electrode,removing the dummy gate pattern after forming the gate silicide toexpose a surface of the substrate in the second active area, and forminga second gate pattern including a second gate insulating layer and ametal gate electrode on the exposed surface of the substrate, the secondgate insulating layer having a thickness smaller than a thickness of thefirst gate insulating layer.

According to an exemplary embodiment of the present invention, a methodfor fabricating a semiconductor device is provided. The method includessequentially forming an insulating layer and a silicon layer on asubstrate, wherein the substrate includes at least one element isolationregion, a first active area and a second active area defined in thesubstrate by the at least one element isolation region, forming a maskpattern including a plurality of openings on the silicon layer, whereinthe openings are formed on the first active area and the second activearea, respectively, patterning the insulating layer and the siliconlayer by etching using the mask pattern as an etching mask to form afirst gate pattern and a dummy gate pattern on the first active area andthe second active area of the substrate, respectively, wherein the firstgate pattern includes a first gate insulating layer and a first silicongate electrode disposed on the first gate insulating layer.

In addition, the method further includes forming a spacer on a sidesurface of the first gate pattern and the dummy gate pattern, forming aburied insulating layer to surround the first gate pattern and the dummygate pattern and expose an upper surface of the first gate pattern andan upper surface of the dummy gate pattern, forming a gate silicide onthe first silicon gate electrode, removing the dummy gate pattern toform a trench in the buried insulating layer to expose a surface of thesubstrate in the second active area, forming a second gate patternincluding a second gate insulating layer and a metal gate electrodesequentially stacked on the exposed surface of the substrate in thetrench in the second active area, wherein the second gate insulatinglayer includes a chemical silicon oxide layer and a high-k gateinsulating layer disposed on the chemical silicon oxide layer, andwherein the second gate insulating layer has a thickness smaller than athickness of the first gate insulating layer and forming a third gatepattern including a third gate insulating layer and a second silicongate electrode sequentially stacked on the at least one elementisolation region of the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention can be understood in moredetail from the following detailed description when taken in conjunctionwith the attached drawings, in which:

FIG. 1 is a cross-sectional view showing a semiconductor device inaccordance with an exemplary embodiment of the present invention;

FIGS. 2 to 10 illustrate intermediate steps for explaining a method forfabricating a semiconductor device in accordance with an exemplaryembodiment of the present invention;

FIG. 11 illustrates an intermediate step for explaining a method forfabricating a semiconductor device in accordance with an exemplaryembodiment of the present invention;

FIGS. 12 to 16 illustrate intermediate steps for explaining a method forfabricating a semiconductor device in accordance with an exemplaryembodiment of the present invention;

FIGS. 17 and 18 illustrate intermediate steps for explaining a methodfor fabricating a semiconductor device in accordance with an exemplaryembodiment of the present invention;

FIG. 19 is a block diagram of a memory card including a semiconductordevice in accordance with an exemplary embodiment of the presentinvention;

FIG. 20 is a block diagram of an information processing system using asemiconductor device in accordance with an exemplary embodiment of thepresent invention; and

FIG. 21 is a block diagram of an electronic apparatus using asemiconductor device in accordance with an exemplary embodiment of thepresent invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present invention will now be describedmore fully hereinafter with reference to the accompanying drawings, inwhich exemplary embodiments of the invention are shown. Exemplaryembodiments of the invention may, however, be embodied in differentforms and should not be construed as limited to exemplary embodimentsset forth herein. In the attached figures, the thickness of layers andregions is exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “connected to,” or “coupled to” another element or layer, it canbe directly connected to or coupled to another element or layer orintervening elements or layers may be present. Like numbers refer tolike elements throughout. As used herein, the term “and/or” includes anyand all combinations of one or more of the associated listed items.

It will also be understood that when a layer is referred to as being“on” another layer or substrate, it can be directly on the other layeror substrate, or intervening layers may also be present.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext.

Hereinafter, a semiconductor device in accordance with an exemplaryembodiment of the present invention will be described with reference toFIG. 1.

FIG. 1 is a cross-sectional view showing a semiconductor device inaccordance with an exemplary embodiment of the present invention.

First, referring to FIG. 1, a semiconductor device 1 includes, forexample, a substrate 10, a first gate pattern 100 and a second gatepattern 200. The semiconductor device 1 may further include, forexample, a third gate pattern 300. Further, although not shown in FIG.1, a silicide pattern may be formed, for example, at both sides of eachof the first gate pattern 100 and the second gate pattern 200, andsource and/or drain contacts may be formed on, for example, the silicidepattern.

Referring to FIG. 1, the semiconductor device 1 includes, for example, afirst element isolation region 12 and a second element isolation region14 isolating active areas on the substrate 10. The first elementisolation region 12 and the second element isolation region 14 havedifferent widths from each other. The substrate 10 includes, forexample, a first active area I and a second active area II defined bythe first and second element isolation regions 12 and 14. Thesemiconductor device 1 includes, for example, the first gate pattern 100formed on the first active area I and the second gate pattern 200 formedon the second active area II. The semiconductor device 1 may furtherinclude, for example, a third gate pattern 300 disposed on the secondelement isolation region 14 whose upper surface has a width larger thanthat of the first element isolation region 12. The first gate pattern100 includes, for example, a first gate insulating layer 110, a firstsilicon gate electrode 120 and a first gate silicide 130, which aresequentially formed on the first active area I. The second gate pattern200 includes, for example, a second gate insulating layer 210 and 220and a metal gate electrode 230, which are sequentially formed on thesecond active area II. The second gate insulating layer 210 and 220 has,for example, a thickness d2 smaller than a thickness d1 of the firstgate insulating layer 110. Here, the “thickness” is a distance from anupper surface 10 s of the substrate to each of the first silicon gateelectrode 120 and the metal gate electrode 230. The third gate pattern300 may include, for example, a third gate insulating layer 310, asecond silicon gate electrode 320 and a second gate silicide 330, whichare sequentially formed on the second element isolation region 14. Thethird gate insulating layer 310 may have, for example, a thickness d3which is equal to, e.g., the thickness d1 of the first gate insulatinglayer 110.

Further, for example, although not shown in FIG. 1, if an upper portionof the substrate 10 contains, e.g., silicon, a silicide pattern may beformed on the first and second active areas I and II not overlappingwith the first gate pattern 100 and the second gate pattern 200.

Referring to FIG. 1, the semiconductor device 1 may further include, forexample, a buried insulating layer 400 formed on the substrate 10. Theburied insulating layer 400 may include, for example, a first trench 100t, a second trench 200 t and a third trench 300 t. For example, thefirst trench 100 t may be formed on the first active area I, the secondtrench 200 t may be formed on the second active area II, and the thirdtrench 300 t may be formed on the second element isolation region 14.The side surfaces of the first to third trenches 100 t, 200 t and 300 tmay be formed of spacers 140, but exemplary embodiments of the presentinvention are not limited thereto. The first gate pattern 100 may beformed in the first trench 100 t, the second gate pattern 200 may beformed in the second trench 200 t, and the third gate pattern 300 may beformed in the third trench 300 t.

For example, the substrate 10 may be made of bulk silicon orsilicon-on-insulator (SOI). Alternatively, the substrate 10 may be asilicon substrate, or include other materials such as silicon germanium,indium antimonide, lead telluride, indium arsenide, indium phosphide,gallium arsenide, or gallium antimonide, but exemplary embodiments ofthe present invention are not limited thereto. Each of the first andsecond element isolation regions 12 and 14 includes, for example, arecess and an insulating pattern including, e.g., an oxide layer fillingup the recess. The first and second element isolation regions 12 and 14may be formed to have, for example, a shallow trench isolation (STI)structure, which may be beneficial to high integration due to, e.g.,excellent element isolation characteristics and small occupation area.The widths of the first and second element isolation regions 12 and 14may vary according to functions. For example, the width of the secondelement isolation region 14 for forming the gate pattern on the elementisolation region may be larger than the width of the first elementisolation region 12 for the isolation characteristics of the element tobe formed on the active area.

The buried insulating layer 400 may include, for example, a first buriedinsulating layer 400 a and a second buried insulating layer 400 b. Thefirst buried insulating layer 400 a formed on the substrate 10 mayinclude, e.g., undoped silicate glass (USG), silicon oxide (SiO₂) or thelike. The second buried insulating layer 400 b formed on the firstburied insulating layer 400 a may be, e.g., a stress liner, andspecifically, may include silicon nitride (SiN). The spacers 140 whichmay constitute the side surfaces of the first to third trenches 100 t,200 t and 300 t may include at least one layer. The spacers 140 mayinclude, e.g., a nitride layer or oxide layer. The spacers 140 may beformed on sidewalls of the first to third gate patterns 100, 200 and300.

Referring to FIG. 1, the first gate pattern 100 formed in the firsttrench 100 t may include, for example, the first gate insulating layer110, the first silicon gate electrode 120 and the first gate silicide130 formed on the substrate 10. The first gate insulating layer 110 andthe first silicon gate electrode 120 that are sequentially stacked areformed, for example, parallel to each other on the upper surface 10 s ofthe substrate. In other words, an interface between the substrate 10 andthe first gate insulating layer 110 is parallel to an interface betweenthe first gate insulating layer 110 and the first silicon gate electrode120. Here, “being parallel to each other” may include not only a casewhere there is the same distance between two surfaces to be compared,but also a case where there is a relatively small difference in distancebetween two surfaces to be compared due to a margin in processing or thelike.

To describe in terms of a fabricating method of the first gate pattern100, the first gate insulating layer 110 and the first silicon gateelectrode 120 may, for example, mean portions formed before forming theburied insulating layer 400. The first gate pattern 100 may be, e.g., ahigh-voltage transistor formed in a peripheral region of thesemiconductor device, but exemplary embodiments of the present inventionare not limited thereto. That is, the first gate pattern 100 may mainlyfunction as a transistor having reliability despite a relatively slowoperating speed rather than a transistor having a relatively fastoperating speed.

The first gate insulating layer 110 may include, e.g., one of a siliconoxide (SiO₂) layer, a silicon oxynitride (SiON) layer and a combinationthereof. A region close to the substrate 10 in the silicon oxide layerincluded in the first gate insulating layer 110 may be formed by, e.g.,thermal oxidation, but exemplary embodiments of the present inventionare not limited thereto. The first silicon gate electrode 120 may bemade of, e.g., polycrystalline silicon or amorphous silicon, butexemplary embodiments of the present invention are not limited thereto.To reduce the resistance of the first silicon gate electrode 120, thefirst silicon gate electrode 120 may include, e.g., impurities. Forexample, the impurities included in the first silicon gate electrode 120may vary according to whether the transistor is a p-type MOS or n-typeMOS transistor. For example, the concentration of impurities may bechanged to adjust the operating characteristics. The first gate silicide130 may include, e.g., any one of nickel (Ni), platinum (Pt), titanium(Ti), ruthenium (Ru), rhodium (Rh), cobalt (Co), hafnium (Hf), tantalum(Ta), erbium (Er), ytterbium (Yb), tungsten (W), or a combinationthereof. The first gate silicide 130 may be formed in, e.g., the firsttrench 100 t.

Referring to FIG. 1, the second gate pattern 200 formed in the secondtrench 200 t may include, for example, the second gate insulating layer210 and 220 and the metal gate electrode 230 formed on the substrate 10.In the semiconductor device of the present exemplary embodiment of thepresent invention, the second gate insulating layer 210 and 220 may beformed, for example, conformally along the bottom surface and both sidesurfaces of the second trench 200 t. In addition, it is noted that thesecond gate insulating layer 210 and 220 may be formed, for example,parallel to the upper surface 10 s of the substrate in accordance withthe fabricating method. In the second gate insulating layer 210 and 220conformally formed in the second trench 200 t, the thickness of thesecond gate insulating layer 210 and 220 formed on the bottom surface ofthe second trench 200 t may be, for example, different from thethickness of the second gate insulating layer 210 and 220 formed on bothside surfaces of the second trench 200 t. The metal gate electrode 230formed on the second gate insulating layer 210 and 220 may be formed ofa single layer, but exemplary embodiments of the present invention arenot limited thereto. Alternatively, the metal gate electrode 230 may beformed of, e.g., a plurality of layers. The metal gate electrode 230formed of a plurality of layers may include, e.g., a metal layerconformally formed on the second gate insulating layer 210 and 220 andboth side surfaces of the second trench 200 t, or a metal layerconformally formed on the second gate insulating layer 210 and 220.

To describe in terms of a fabricating method of the second gate pattern200, the second gate insulating layer 210 and 220 and the metal gateelectrode 230 may be formed, e.g., after forming the buried insulatinglayer 400. Not to mention that, for example, only the metal gateelectrode 230 may be formed after forming the buried insulating layer400. The second gate pattern 200 may be, e.g., a low-voltage transistorformed in a main region of the semiconductor device, but exemplaryembodiments of the present invention are not limited thereto. That is,the second gate pattern 200 may mainly function as a transistor having arelatively fast operating speed rather than a transistor havingreliability.

The second gate insulating layer 210 and 220 may include, e.g., achemical silicon oxide layer 210 and a high dielectric constant (high-k)gate insulating layer 220. The high-k gate insulating layer 220 mayinclude, e.g., at least one of hafnium oxide, hafnium silicon oxide,lanthanum oxide, lanthanum aluminum oxide, zirconium oxide, zirconiumsilicon oxide, tantalum oxide, titanium oxide, barium strontium titaniumoxide, barium titanium oxide, strontium titanium oxide, yttrium oxide,aluminum oxide, lead scandium tantalum oxide, and lead zinc niobate. Themetal gate electrode 230 may be formed of a single layer or multiplelayers including, e.g., hafnium (Hf), zirconium (Zr), titanium (Ti),tantalum (Ta), aluminum (Al) and/or an alloy thereof. For example, themetal gate electrode 230 may have a structure of five layers of titaniumnitride (TiN)-tantalum nitride (TaN)-titanium aluminum (TiAl)-titaniumnitride (TiN)-titanium (Ti)/aluminum (Al).

Referring to FIG. 1, the third gate pattern 300 formed in the thirdtrench 300 t may have the same structure as, e.g., the first gatepattern 100. In other words, the third gate insulating layer 310 and thesecond silicon gate electrode 320 that are sequentially stacked may beformed parallel to each other on the upper surface of the second elementisolation region 14. In the same way as the first gate pattern 100, thethird gate pattern 300 may be formed, e.g., before forming the buriedinsulating layer 400. The third gate pattern 300 formed on the secondelement isolation region 14 may be, e.g., a resistor or e-fuse, butexemplary embodiments of the present invention are not limited thereto.The third gate insulating layer 310, the second silicon gate electrode320 and the second gate silicide 330 may be made of, e.g., the samematerials as those of the first gate insulating layer 110, the firstsilicon gate electrode 120 and the first gate silicide 130,respectively. However, the impurities included in the second silicongate electrode 320 may be, for example, different from the impuritiesincluded in the first silicon gate electrode 120 and may include, e.g.,p-type impurities.

A metal-oxide-semiconductor (MOS) transistor using a silicon gateelectrode is widely known. As various process parameters for fabricatinga transistor using silicon as a gate electrode have been established,processing reliability may be ensured. However, as a silicon materialusually has a resistance higher than that of a metal material, thesilicon gate electrode operates at a speed lower than the gate made of ametal material. Meanwhile, the gate made of a metal material operates ata relatively fast speed, but may have processing reliability lower thanthe silicon gate electrode because less process parameters areestablished than the gate using the silicon gate electrode. Thesemiconductor device 1 according to the present exemplary embodiment ofthe present invention making up for this drawback may have benefits interms of various aspects. For example, first, as residues of aphotosensitive film or the like can be prevented from entering betweenthe gate electrode and the gate insulating layer in, e.g., ahigh-voltage transistor requiring a stable operation, it is possible toensure the reliability of the semiconductor device. Further, by using awell-established silicon gate electrode process, various electricaldesign parameters such as a resistor of the gate electrode may be usedas they are. Accordingly, a transistor requiring a stable operation canbe implemented directly without a change in design.

A method for fabricating a semiconductor device in accordance with anexemplary embodiment of the present invention will be described withreference to FIGS. 2 to 10. As the third gate pattern 300 shown in FIG.1 is fabricated by the same fabricating method as the first gate pattern100, a description of the fabricating method of the third gate pattern300 will be omitted.

FIGS. 2 to 10 illustrate intermediate steps for explaining a method forfabricating a semiconductor device in accordance with an exemplaryembodiment of the present invention.

Referring to FIG. 2, the first and second element isolation regions 12and 14 defining the first active area I and the second active area IIare formed on the substrate 10. An insulating layer 20 and a siliconlayer 22 are sequentially formed on the substrate 10 on which the firstand second element isolation regions 12 and 14 are formed. The substrate10 may be made of, for example, bulk silicon or silicon-on-insulator(SOD. Alternatively, the substrate 10 may be, for example, a siliconsubstrate, or include other materials such as silicon germanium, indiumantimonide, lead telluride, indium arsenide, indium phosphide, galliumarsenide, or gallium antimonide, but exemplary embodiments of thepresent invention are not limited thereto. In the method for fabricatingthe semiconductor device according to the present invention, a casewhere the substrate 10 is a silicon substrate will be described as anexample. The first and second element isolation regions 12 and 14 may bean insulating pattern including, e.g., silicon oxide. The widths of thefirst and second element isolation regions 12 and 14 may vary accordingto purposes. Although a case where the upper surfaces of the first andsecond element isolation regions 12 and 14 and the upper surface of thesubstrate 10 are located on the same plane has been illustrated in FIG.2, exemplary embodiments of the present invention are not limitedthereto.

The insulating layer 20 may include, e.g., one of a silicon oxide (SiO₂)layer, a silicon oxynitride (SiON) layer and a combination thereof. Theinsulating layer 20 may be formed by, e.g., thermal treatment, chemicalmaterial treatment, atomic layer deposition (ALD), chemical vapordeposition (CVD) or the like.

The silicon layer 22 may include, e.g., one of polycrystalline silicon(poly Si), amorphous silicon (a-Si) and a combination thereof. Thepolycrystalline silicon may be formed by, e.g., CVD and the amorphoussilicon may be formed by using, e.g., sputtering, CVD, plasma depositionor the like, but exemplary embodiments of the present invention are notlimited thereto. The silicon layer 22 may include, e.g., impurities. Theimpurities included in the silicon layer 22 may be, for example, p-typeimpurities or n-type impurities according to, e.g., the type oftransistor. The silicon layer 22 may be formed to include impurities,e.g., by ion implantation 24 after forming the silicon layer 22.Alternatively, the silicon layer 22 may be formed to include impurities,e.g., by doping impurities in-situ while forming the silicon layer 22,but exemplary embodiments of the present invention are not limitedthereto.

After forming the silicon layer 22, a photosensitive film pattern (notshown) including a plurality of openings is formed on the silicon layer22 (see FIG. 2). The openings included in the photosensitive filmpattern are formed on the first active area I and the second active areaII respectively. The photosensitive film pattern is removed afteretching the insulating layer 20 and the silicon layer 22 by using, forexample, the photosensitive film pattern formed on the silicon layer 22.In other words, the insulating layer 20 and the silicon layer 22 arepatterned.

Referring to FIG. 3, the patterned insulating layer and silicon layerbecome the first gate pattern 100 and a dummy gate pattern 500respectively. That is, the first gate pattern 100 is formed on the firstactive area I and the dummy gate pattern 500 is formed on the secondactive area II. The first gate pattern 100 and the dummy gate pattern500 have, for example, the same structure, but the dummy gate pattern500 is removed in the subsequent step. For example, the spacers 140 maybe formed on the side surfaces of the first gate pattern 100 and thedummy gate pattern 500. The spacers 140 may include, e.g., siliconoxide, silicon nitride or the like. The spacers 140 may be formed on theside surfaces of the first gate pattern 100 and the dummy gate pattern500 by forming a spacer film (not shown) using, e.g., a CVD process andthen performing etch-back on the spacer film.

The first gate pattern 100 includes, for example, the first gateinsulating layer 110 and the first silicon gate electrode 120. In thesame way as the insulating layer 20 of FIG. 2, the first gate insulatinglayer 110 may include, e.g., one of a silicon oxide (SiO₂) layer, asilicon oxynitride (SiON) layer and a combination thereof. Further, thefirst gate insulating layer 110 may have the thickness d1. In the sameway as the silicon layer 22 of FIG. 2, the first silicon gate electrode120 may be made of, e.g., polycrystalline silicon or amorphous silicon,but exemplary embodiments of the present invention are not limitedthereto. If the silicon layer 22 includes impurities, the first silicongate electrode 120 may also includes impurities.

For example, referring to FIG. 4, the buried insulating layer 400 isformed to surround the first gate insulating layer 110 and the dummygate pattern 500. The buried insulating layer 400 exposes the first gatepattern 100 and the dummy gate pattern 500. For example, the buriedinsulating layer 400 is formed on the first gate pattern 100 and thedummy gate pattern 500. The height of the buried insulating layer 400is, for example, at least higher than those of the first gate pattern100 and the dummy gate pattern 500. Then, the upper surface of the firstgate pattern 100 and the upper surface of the dummy gate pattern 500 areexposed by, for example, partially removing the buried insulating layer400. The method of partially removing the buried insulating layer 400includes, for example, planarizing the buried insulating layer 400 untilsilicon of the first gate pattern 100 and the dummy gate pattern 500 isexposed by, e.g., chemical mechanical polishing (CMP).

If the silicon layer 22 does not include impurities in FIG. 2, theimpurities may be, for example, implanted into the planarized buriedinsulating layer 400, the first gate pattern 100 and the dummy gatepattern 500 by, e.g., the ion implantation 24. That is, the resistanceof the first silicon gate electrode 120 can be reduced by implantingimpurities into the first silicon gate electrode 120 through ionimplantation. The impurities included in the first silicon gateelectrode 120 may be p-type impurities or n-type impurities accordingto, e.g., the type of transistor.

The buried insulating layer 400 may include, for example, the firstburied insulating layer 400 a and the second buried insulating layer 400b. The first buried insulating layer 400 a may include, e.g., undopedsilicate glass (USG), silicon oxide (SiO₂) or the like. The secondburied insulating layer 400 b may be, e.g., a stress liner, and mayinclude, for example, silicon nitride (SiN).

Referring to FIG. 5, a photosensitive film pattern 30 is formed on theburied insulating layer 400. The photosensitive film pattern 30includes, for example, an opening 30 i and the opening 30 i is formed onthe exposed dummy gate pattern 500. For example, the photosensitive filmpattern 30 may protect the first active area I and expose the secondactive area II. The opening 30 i may expose, for example, a portion ofthe upper surface of the buried insulating layer 400 and the uppersurface of the dummy gate pattern 500. The first silicon gate electrode120 included in the first gate pattern 100 is protected by thephotosensitive film pattern 30. The photosensitive film pattern 30 maybe, e.g., a mask pattern to be used in the subsequent etching step.

Referring to FIG. 6, the dummy gate pattern 500 is removed by, forexample, using the photosensitive film pattern 30 (see FIG. 5) as anetching mask to form the second trench 200 t in the buried insulatinglayer 400. When the second trench 200 t is formed in the buriedinsulating layer 400, the surface 10 s of the substrate 10 of the secondactive area II may be exposed. In the method of fabricating asemiconductor device according to the present exemplary embodiment ofthe present invention, a case where the surface 10 s of the substrate isexposed by the second trench 200 t will be described, but exemplaryembodiments of the present invention are not limited thereto. Afterexposing the surface 10 s of the substrate 10 of the second active areaII, the photosensitive film pattern 30 used as an etch mask is removed.

A dummy silicon electrode 520 (see FIG. 5) included in the dummy gatepattern 500 exposed by the opening 30 i is removed by, for example, anetching process. As an etching process for removing the dummy siliconelectrode 520, a wet etching process using, e.g., ammonia, tetramethylammonium hydroxide (TMAH) and/or tetraethylammonium hydroxide (TEAH) maybe used, but exemplary embodiments of the present invention are notlimited thereto. A dummy gate insulating layer 510 (see FIG. 5) exposedafter removing the dummy silicon electrode 520 is also removed through,for example, an etching process. The dummy gate insulating layer 510 maybe removed by, for example, wet etching, dry etching and a combinationthereof. The etching solution or etching gas may be changed according tothe material of the dummy gate insulating layer 510.

Referring to FIG. 7, the chemical silicon oxide layer 210, a high-kinsulating layer 220 a and a metal layer 230 a are sequentially formedin the second trench 200 t. For example, the chemical silicon oxidelayer 210 is grown by a chemical method on the exposed surface of thesubstrate 10. The chemical silicon oxide layer 210 may be, for example,formed conformally on the bottom surface of the second trench 200 t. Thechemical silicon oxide layer 210 may serve as, e.g., an interfaciallayer between the substrate 10 and the high-k insulating layer 220 a tobe formed subsequently. The high-k insulating layer 220 a is formed onthe chemical silicon oxide layer 210. The high-k insulating layer 220 amay be formed, for example, conformally on, e.g., both side surfaces ofthe second trench 200 t, and the upper surface of the chemical siliconoxide layer 210 and the upper surface of the buried insulating layer400. The metal layer 230 a is formed on the conformally formed high-kinsulating layer 220 a. The metal layer 230 a is deposited to fill upthe second trench 200 t.

The chemical silicon oxide layer 210 may be formed, e.g., by processingthe substrate 10 using a chemical material. For example, in the case ofprocessing the substrate 10 using a solution including an oxygen sourceand ammonia (NH₃), a specific region of the substrate 10 may be oxidizedby the oxygen source to form the chemical silicon oxide layer 210. Inthis case, hydrogen peroxide may be used as the oxygen source, butexemplary embodiments of the present invention are not limited thereto.

The high-k insulating layer 220 a may include, e.g., at least one ofhafnium oxide, hafnium silicon oxide, lanthanum oxide, lanthanumaluminum oxide, zirconium oxide, zirconium silicon oxide, tantalumoxide, titanium oxide, barium strontium titanium oxide, barium titaniumoxide, strontium titanium oxide, yttrium oxide, aluminum oxide, leadscandium tantalum oxide, and lead zinc niobate, but exemplaryembodiments of the present invention are not limited thereto. The high-kinsulating layer 220 a may be formed by, e.g., CVD, physical vapordeposition (PVD), or atomic layer deposition (ALD).

Although the metal layer 230 a is illustrated as a single layer in FIG.7, exemplary embodiments of the present invention are not limitedthereto. The metal layer 230 a may be formed of, for example, a singlelayer or multiple layers including, e.g., hafnium (Hf), zirconium (Zr),titanium (Ti), tantalum (Ta), aluminum (Al) and/or an alloy thereof. Forexample, the metal layer 230 a may have a structure of five layers ofTiN—TaN—TiAl—TiN—Ti/Al. The metal layer 230 a may be formed by, e.g.,CVD, PVD, or ALD.

Referring to FIGS. 7 and 8, the upper surface of the first gate pattern100, e.g., the silicon gate electrode 120 is exposed by removing aportion of the metal layer 230 a and a portion of the high-k insulatinglayer 220 a. Accordingly, the second gate pattern 200 is formed on thesurface of the substrate exposed in the second trench 200 t. The secondgate pattern 200 includes, for example, the second gate insulating layer210 and 220 and the metal gate electrode 230. The second gate insulatinglayer 210 and 220 includes, for example, the chemical silicon oxidelayer 210 and the high-k gate insulating layer 220. In the method forfabricating a semiconductor device according to the present exemplaryembodiment of the present invention, a case of removing both a portionof the metal layer 230 a and a portion of the high-k insulating layer220 a has been described, but exemplary embodiments of the presentinvention are not limited thereto. That is, the metal gate electrode 230may be formed, for example, after forming the high-k gate insulatinglayer 220 by removing a portion of the high-k insulating layer 220 a.

The thickness d1 of the first gate insulating layer 110 included in thefirst gate pattern 100 is, for example, larger than the thickness d2 ofthe second gate insulating layer 210 and 220 included in the second gatepattern 200. However, a dielectric constant of the first gate insulatinglayer 110 may be, for example, smaller than a dielectric constant of thesecond gate insulating layer 210 and 220. The high-k gate insulatinglayer 220 included in the second gate insulating layer 210 and 220 maybe formed, for example, conformally on both side surfaces and bottomsurface of the second trench 200 t.

Referring to FIG. 9, a mask pattern 40 b is formed on the first gatepattern 100, the second gate pattern 200 and the buried insulating layer400. The mask pattern 40 b includes, for example, first contact holes h1and a second contact hole h2. The first contact holes h1 and the secondcontact hole h2 may be formed, for example, simultaneously in the maskpattern 40 b. The first contact holes h1 are formed to, for example,pass through the mask pattern 40 b and the buried insulating layer 400.The first contact holes h1 are formed, for example, at both sides of thefirst gate pattern 100 and the second gate pattern 200. The firstcontact holes h1 may expose, for example, a surface 10 a of thesubstrate at both sides of the first gate pattern 100 and the secondgate pattern 200. The second contact hole h2 may be formed, for example,on the first silicon gate electrode 120 to expose the upper surface ofthe first silicon gate electrode 120.

Referring to FIG. 10, a metal layer (not shown) for forming a silicideis formed on the mask pattern 40 b. The metal layer is formed, forexample, conformally on the upper surface of the mask pattern 40 b, thesilicon gate electrode 120 and the surface 10 a of the substrate (seeFIG. 9) exposed by the first contact holes h1 and the second contacthole h2. Then, for example, a thermal treatment may be performed toallow the silicon gate electrode 120 to react with the surface 10 a ofthe substrate 10 exposing the metal layer for forming a silicide. Thefirst gate silicide 130 may be formed on the silicon gate electrode 120by, for example, thermal treatment of the metal layer. If the substrate10 is, e.g., a silicon substrate, when forming the first gate silicide130, a silicide pattern 600 may be formed, for example, simultaneouslyon the exposed substrate surface. That is, the silicide pattern 600being formed in the first contact holes h1 may be formed, for example,at the same time as the first gate silicide 130. After forming the firstgate silicide 130 and the silicide pattern 600, the unreacted metallayer is removed.

The gate silicide 130 and the silicide pattern 600 may include, e.g.,any one of Ni, Pt, Ti, Ru, Rh, Co, Hf, Ta, Er, Yb and W, or acombination thereof. The metal layer for forming a silicide may bedeposited by, e.g., CVD, PVD, ALD or sputtering.

A method for fabricating a semiconductor device in accordance with anexemplary embodiment of the present invention will be described withreference to FIG. 11. As this embodiment is substantially the same asthe above-described methods discussed in connection with FIGS. 2 to 10except for a method for forming a mask pattern for forming a gatesilicide, the same reference numerals are assigned to the samecomponents as those of the above-described method in connection withFIGS. 2 to 10, and thus a description thereof will be simplified oromitted.

FIG. 11 illustrates an intermediate step for explaining a method forfabricating a semiconductor device in accordance with an exemplaryembodiment of the present invention.

Referring to FIG. 11, a pre-mask pattern 40 a is formed on the firstgate pattern 100, the second gate pattern 200 and the buried insulatinglayer 400. The pre-mask pattern 40 a includes, for example, the firstcontact holes h1. The first contact holes h1 are formed to, for example,pass through the pre-mask pattern 40 a and the buried insulating layer400. The first contact holes h1 are formed, for example, at both sidesof the first gate pattern 100 and the second gate pattern 200. The firstcontact holes h1 may expose, for example, the surface 10 a of thesubstrate 10 at both sides of the first gate pattern 100 and the secondgate pattern 200.

After forming the pre-mask pattern 40 a including the first contactholes h1, the second contact hole h2 is formed. Accordingly, the maskpattern 40 b is formed on the first gate pattern 100, the second gatepattern 200 and the buried insulating layer 400. The second contact holeh2 may be formed on, for example, the first silicon gate electrode 120to expose the upper surface of the first silicon gate electrode 120 insubstantially the same manner as set forth in FIG. 10.

A method for fabricating a semiconductor device in accordance with anexemplary embodiment of the present invention will be described withreference to FIGS. 12 to 16. As this embodiment has the same structureas that of FIGS. 2 to 4, a redundant description thereof will be omittedby assigning the same reference numerals.

FIGS. 12 to 16 illustrate intermediate steps for explaining a method forfabricating a semiconductor device in accordance with an exemplaryembodiment of the present invention.

In the present exemplary embodiment, after performing the methodillustrated in FIGS. 2 to 4, then the method illustrated in FIGS. 12 to16 may be performed.

For example, referring to FIG. 12, a blocking pattern 50 is formed onthe buried insulating layer 400. The blocking pattern 50 includes, forexample, a first opening 50 i, and the first opening 50 i is formed onthe exposed first gate pattern 100. For example, the blocking pattern 50covers the second active area II and exposes the first active area I.The first opening 50 i exposes, for example, a portion of the uppersurface of the buried insulating layer 400 and the upper surface of thefirst gate pattern 100, e.g., the first silicon gate electrode 120. Theblocking pattern 50 may be, e.g., a mask pattern to be used in thesubsequent step for forming a silicide.

After forming the blocking pattern 50, the first gate silicide 130 isformed on the first silicon gate electrode 120. For example, a metallayer (not shown) is formed on the blocking pattern 50 and the firstgate pattern 100. Then, the first gate silicide 130 is formed on thefirst silicon gate electrode 120 by performing, for example, a thermaltreatment on the metal layer. The first gate silicide 130 and the dummygate pattern 500 are exposed by, for example, removing the unreactedmetal layer and the blocking pattern 50. Although a case where the firstgate silicide 130 protrudes from the upper surface of the buriedinsulating layer 400 has been illustrated in FIG. 12, exemplaryembodiments of the present invention are not limited thereto.

Referring to FIG. 13, the photosensitive film pattern 30 is formed onthe buried insulating layer 400 and the gate silicide 130. Thephotosensitive film pattern 30 includes, for example, a second opening30 i and the second opening 30 i is formed on the exposed dummy gatepattern 500. For example, the photosensitive film pattern 30 may protectthe first active area I and expose the second active area II. Thephotosensitive film pattern 30 may be, e.g., a mask pattern to be usedin the subsequent etching step.

Referring to FIG. 14, the dummy gate pattern 500 is removed by, forexample, using the photosensitive film pattern 30 as an etching mask toform the second trench 200 t in the buried insulating layer 400. Whenthe second trench 200 t is formed in the buried insulating layer 400,the surface 10 s of the substrate 10 of the second active area II may beexposed. Both side surfaces of the second trench 200 t may be formed bythe spacers 140. The dummy gate pattern 500 exposed by the secondopening 30 i is removed by, for example, an etching process. Afterremoving the dummy gate pattern 500, the photosensitive film pattern 30is removed.

Referring to FIG. 15, the chemical silicon oxide layer 210, the high-kinsulating layer 220 a and the metal layer 230 a are sequentially formedin the second trench 200 t. For example, the chemical silicon oxidelayer 210 is grown conformally by a chemical method on the exposedsurface of the substrate 10. The chemical silicon oxide layer 210 mayserve as, e.g., an interfacial layer between the substrate 10 and thehigh-k gate insulating layer 220 a. The high-k insulating layer 220 a isformed on the chemical silicon oxide layer 210. The high-k insulatinglayer 220 a may be formed, for example, conformally on, e.g., both sidesurfaces of the second trench 200 t, and the chemical silicon oxidelayer 210 and the first gate silicide 130. The metal layer 230 a coversthe high-k insulating layer 220 a and the first gate silicide 130. Themetal layer 230 a is deposited to fill up the second trench 200 t.

Referring to FIGS. 15 and 16, the first gate silicide 130 is exposed by,for example, removing a portion of the metal layer 230 a and a portionof the high-k insulating layer 220 a. Accordingly, the second gateinsulating layer 210 and 220 and the metal gate electrode 230 are formedon the surface of the substrate 10 exposed in the second trench 200 t.The second gate insulating layer 210 and 220 includes, for example, thechemical silicon oxide layer 210 and the high-k gate insulating layer220. The thickness d1 of the first gate insulating layer 110 included inthe first gate pattern 100 is, for example, larger than the thickness d2of the second gate insulating layer 210 and 220 included in the secondgate pattern 200.

A method for fabricating a semiconductor device in accordance with anexemplary embodiment of the present invention will be described withreference to FIGS. 17 and 18. As this exemplary embodiment issubstantially the same as the method of FIGS. 12 to 16 except for theformation of a dummy silicide, the same reference numerals are assignedto the same components as those of the above-described method of FIGS.12 to 16, and thus a description thereof will be simplified or omitted.

FIGS. 17 and 18 illustrate intermediate steps for explaining a methodfor fabricating a semiconductor device in accordance with an exemplaryembodiment of the present invention.

Referring to FIG. 17, the dummy gate pattern 500 includes, for example,the dummy gate insulating layer 510 and the dummy silicon electrode 520that are sequentially formed. After planarizing the buried insulatinglayer 400, when the first gate silicide 130 is formed on the firstsilicon gate electrode 120, a dummy silicide 530 is formed, for example,simultaneously on the dummy silicon electrode 520.

Referring to FIG. 18, the photosensitive film pattern 30 is formed onthe buried insulating layer 400 and the first gate silicide 130. Thephotosensitive film pattern includes, for example, the opening 30 iexposing the dummy silicide 530. The dummy gate pattern 500 includingthe dummy silicide 530 is removed by, for example, using thephotosensitive film pattern 30 as a mask pattern of the etching process.As the formation of the second gate pattern 200 in the second trench 200t formed by removing the dummy gate pattern 500 is the same as describedabove in connection with FIGS. 14 to 16, a description thereof will beomitted.

FIG. 19 is a block diagram of a memory card including a semiconductordevice in accordance with an exemplary embodiment of the presentinvention.

Referring to FIG. 19, a memory 1210 including a semiconductor devicefabricated in accordance with exemplary embodiments of the presentinvention may be employed in a memory card 1200. The memory card 1200may include, for example, a memory controller 1220 for controlling dataexchange between a host 1230 and the memory 1210. An SRAM 1221 may beused as an operation memory of a central processing unit (CPU) 1222. Ahost interface (I/F) 1223 may include, for example, a protocol allowingthe host 1230 to be connected with the memory card 1200 for dataexchange. An error correction code (ECC) 1224 may detect and correct anerror of data read from the memory 1210. A memory interface (I/F) 1225may interface with the memory 1210. The CPU 1222 may perform a wholecontrol operation associated with data exchange of the memory controller1220.

FIG. 20 is a block diagram of an information processing system using asemiconductor device in accordance with an exemplary embodiment of thepresent invention.

Referring to FIG. 20, an information processing system 1300 may include,for example, a memory system 1310 including a semiconductor devicefabricated in accordance with exemplary embodiments of the presentinvention. The information processing system 1300 may include, forexample, the memory system 1310, a modem 1320, a central processing unit(CPU) 1330, a RAM 1340 and a user interface (I/F) 1350, which areelectrically connected to a system bus 1360. The memory system 1310 mayinclude, for example, a memory 1311 and a memory controller 1312, andmay have substantially the same configuration as that of the memory card1200 shown in FIG. 19. The data being processed by the CPU 1330 or thedata being received from an external apparatus may be stored in thememory system 1310. The information processing system 1300 may beapplied to, for example, a memory card, solid state disk (SSD), cameraimage sensor and other various chipsets. For example, the memory system1310 may be configured to employ a solid state disk (SSD) such that theinformation processing system 1300 can stably and reliably processlarge-capacity data.

FIG. 21 is a block diagram of an electronic apparatus using thesemiconductor device in accordance with an exemplary embodiment of thepresent invention.

Referring to FIG. 21, an electronic apparatus 1400 may include, forexample, a semiconductor device fabricated in accordance with exemplaryembodiments of the present invention. The electronic apparatus 1400 maybe used in, for example, a wireless communication apparatus (e.g., PDA,laptop computer, mobile computer, web tablet, wireless phone, and/orwireless digital music player) or in various apparatuses that cantransmit and receive information in a wireless communicationenvironment.

The electronic apparatus 1400 may include, for example, a controller1410, an input/output unit (I/O) 1420, a memory 1430, and a wirelessinterface 1440. In this case, the memory 1430 may include, for asemiconductor device fabricated in accordance with exemplary embodimentsof the present invention. The controller 1410 may include, for example,a processor such as a microprocessor and digital signal processor. Thememory 1430 may be used to store a command (or user data) to beprocessed by the controller 1410. The wireless interface 1440 may beused to transmit/receive data through a wireless data network. Thewireless interface 1440 may include, for example, an antenna and/orwireless transceiver. The electronic apparatus 1400 may use, forexample, a protocol of a third generation communication system such ascode division multiple access (CDMA) communication system, global systemfor mobile communication (GSM), North American dual mode cellular(NADC), Evolutionary-TDMA Scheduling Protocol (E-TDMA), wideband codedivision multiple access (WCDMA), and code division multiple access 2000(CDMA2000).

Having described exemplary embodiments of the present invention, it isfurther noted that it is readily apparent to those of ordinary skill inthe art that various modifications may be made without departing fromthe spirit and scope of the invention which is defined by the metes andbounds of the appended claims.

What is claimed is:
 1. A method for fabricating a semiconductor device,comprising: forming a first gate pattern and a dummy gate pattern on afirst active area and a second active area of a substrate, respectively,wherein the first gate pattern includes a first gate insulating layerand a silicon gate electrode; removing the dummy gate pattern to exposea surface of the substrate in the second active area; forming a secondgate pattern including a second gate insulating layer and a metal gateelectrode on the exposed surface of the substrate, wherein the firstgate insulating layer has a thickness larger than a thickness of thesecond gate insulating layer; and forming a gate silicide on the silicongate electrode after forming the second gate pattern.
 2. The method ofclaim 1, wherein the removing of the dummy gate pattern comprises:forming a buried insulating layer to surround the first gate pattern andthe dummy gate pattern and expose the first gate pattern and the dummygate pattern; and forming a trench in the buried insulating layer byetching the exposed dummy gate pattern.
 3. The method of claim 2,wherein after forming the buried insulating layer, the method furthercomprising: forming a mask pattern including an opening on the buriedinsulating layer, wherein the opening being formed on the exposed dummygate pattern; and forming the trench in the buried insulating layer toexpose the surface of the substrate by etching using the mask pattern asan etching mask.
 4. The method of claim 2, wherein the forming of thesecond gate pattern comprises: forming a high dielectric constant(high-k) insulating layer on a bottom surface and on opposing sidesurfaces of the trench; forming a metal layer to cover the high-kinsulating layer and the first gate pattern; and forming the second gateinsulating layer and the metal gate electrode in the trench by removinga portion of the metal layer and the high-k insulating layer to exposean upper surface of the first gate pattern.
 5. The method of claim 1,wherein the forming of the gate silicide comprises forming a maskpattern including a plurality of first contact holes and a secondcontact hole on the first gate pattern and the second gate pattern,wherein the first contact holes are formed at opposing sides of thefirst gate pattern and the second gate pattern, and wherein the secondcontact hole is formed on the silicon gate electrode.
 6. The method ofclaim 5, wherein the first contact holes and the second contact hole areformed simultaneously.
 7. The method of claim 5, wherein the substrateis a silicon substrate, and wherein a silicide pattern is formed in thefirst contact holes simultaneously with the gate silicide.
 8. The methodof claim 1, wherein the forming of the first gate pattern and the dummygate pattern comprises: sequentially forming an insulating layer and asilicon layer on the substrate; forming a mask pattern including aplurality of openings on the silicon layer, wherein the openings areformed on the first and second active areas respectively; and patterningthe insulating layer and the silicon layer by etching using the maskpattern as an etching mask.
 9. The method of claim 8, wherein beforeforming the mask pattern, the method further comprising: implantingimpurities into the silicon layer by ion implantation.
 10. The method ofclaim 8, wherein between forming the first gate pattern and removing thedummy gate pattern, the method further comprising: implanting impuritiesinto the silicon gate electrode by ion implantation.
 11. A method forfabricating a semiconductor device, comprising: forming a first gatepattern and a dummy gate pattern on a first active area and a secondactive area of a substrate, respectively, wherein the first gate patternincludes a first gate insulating layer and a silicon gate electrode;forming a gate silicide on the silicon gate electrode; removing thedummy gate pattern after forming the gate silicide to expose a surfaceof the substrate in the second active area; and forming a second gatepattern including a second gate insulating layer and a metal gateelectrode on the exposed surface of the substrate, wherein the secondgate insulating layer has a thickness smaller than a thickness of thefirst gate insulating layer.
 12. The method of claim 11, wherein beforeforming the gate silicide, the method further comprising: forming aburied insulating layer to surround the first gate pattern and the dummygate pattern and expose the first gate pattern and the dummy gatepattern; and forming a first mask pattern including a first opening onthe silicon gate electrode of the exposed first gate pattern.
 13. Themethod of claim 12, wherein the removing of the dummy gate patterncomprises: forming a second mask pattern including a second opening onthe gate silicide and the buried insulating layer, wherein the secondopening is formed on the dummy gate pattern; and forming a trench in theburied insulating layer by etching using the second mask pattern as anetching mask.
 14. The method of claim 13, wherein the forming of thesecond gate pattern comprises: forming a high dielectric constant(high-k) insulating layer on a bottom surface and on opposing sidesurfaces of the trench; forming a metal layer to cover the high-kinsulating layer and the gate silicide; and forming the second gateinsulating layer and the metal gate electrode in the trench by removinga portion of the metal layer and the high-k insulating layer to exposean upper surface of the gate silicide.
 15. The method of claim 11,wherein the dummy gate pattern includes a dummy gate insulating layerand a dummy silicon electrode that are sequentially formed, and whereinwhen forming the gate silicide, a dummy silicide is formedsimultaneously on the dummy silicon electrode.
 16. A method forfabricating a semiconductor device, comprising: sequentially forming aninsulating layer and a silicon layer on a substrate, wherein thesubstrate includes at least one element isolation region, a first activearea and a second active area defined in the substrate by the at leastone element isolation region; forming a mask pattern including aplurality of openings on the silicon layer, wherein the openings areformed on the first active area and the second active area,respectively; patterning the insulating layer and the silicon layer byetching using the mask pattern as an etching mask to form a first gatepattern and a dummy gate pattern on the first active area and the secondactive area of the substrate, respectively, wherein the first gatepattern includes a first gate insulating layer and a first silicon gateelectrode disposed on the first gate insulating layer; forming a spaceron a side surface of the first gate pattern and the dummy gate pattern;forming a buried insulating layer to surround the first gate pattern andthe dummy gate pattern and expose an upper surface of the first gatepattern and an upper surface of the dummy gate pattern; forming a gatesilicide on the first silicon gate electrode; removing the dummy gatepattern to form a trench in the buried insulating layer to expose asurface of the substrate in the second active area; forming a secondgate pattern including a second gate insulating layer and a metal gateelectrode sequentially stacked on the exposed surface of the substratein the trench in the second active area, wherein the second gateinsulating layer includes a chemical silicon oxide layer and a high-kgate insulating layer disposed on the chemical silicon oxide layer, andwherein the second gate insulating layer has a thickness smaller than athickness of the first gate insulating layer; and forming a third gatepattern including a third gate insulating layer and a second silicongate electrode sequentially stacked on the at least one elementisolation region of the substrate.
 17. The method of claim 16, whereinthe third gate pattern is formed before the forming of the buriedinsulating layer, and wherein the third gate insulating layer and thesecond silicon gate electrode of the third gate pattern are formed of asame material as the first gate insulating layer and the first silicongate electrode of the first gate pattern, respectively.
 18. The methodof claim 16, wherein the first silicon gate electrode of the first gatepattern and the second silicon gate electrode of the third gate patterneach include a different impurity from each other.
 19. The method ofclaim 16, wherein the gate silicide is formed on the first silicon gateelectrode after forming the second gate pattern.
 20. The method of claim16, wherein the forming of the second gate pattern comprises:sequentially forming the chemical silicon oxide layer, a high-kinsulating layer and a metal layer in the trench, wherein the chemicalsilicon oxide layer is conformably formed on a bottom surface of thetrench, wherein the high-k insulating layer is conformably formed onopposing side surfaces of the trench, an upper surface of the chemicalsilicon oxide layer and on an upper surface of the buried insulatinglayer and wherein the metal layer is conformably formed on the high-kinsulating layer and fills up the trench; and removing a portion of themetal layer and a portion of the high-k insulating layer.